Over the years I've spent a fair bit of time hanging round the world's airports between flights. But I've only once actually forked out the money to stay at a hotel there.
That was in Delhi, when the company I was travelling with said very firmly that it would not be safe to spend the night at the terminal, and booked me a room nearby.
Unfortunately, it wasn't particularly safe getting to the room either, because my taxi driver caused an accident, got into a fight with the other driver, drove through some roadworks, tried to force me to stay at a different hotel ... and then had the gall to demand a tip.
I didn't get much sleep, due to a combination of being a bit wound up as a result of that experience, suffering from jetlag and spending most of the night worrying whether the alarm would work.
Apart from that, thanks to my basic tightfistedness and a feeling that I probably wouldn't get much rest for my money, I've usually spent any lengthy stopovers at the airport and done my best to fill in the time.